IAC: False Positives Common Post-HIV Vaccination

In second study, non-targeted opt-out HIV screening in ER shows only modest benefits

By Eric Metcalf

HealthDay Reporter

MONDAY, July 19 (HealthDay News) -- The use of HIV vaccines commonly leads to vaccine-induced seropositivity/reactivity (VISP), and non-targeted opt-out HIV screening in emergency departments is linked to identification of a modestly increased number of patients with new HIV diagnoses compared to diagnostic testing, according to two studies published in the July 21 issue of the Journal of the American Medical Association to coincide with presentation at the International AIDS Conference, held from July 18 to 23 in Vienna, Austria.

Cristine J. Cooper, Ph.D., of the Fred Hutchinson Cancer Research Center in Seattle, and colleagues analyzed data from 2,176 participants free of HIV who were vaccinated. They used three common enzyme immunoassay (EIA) HIV antibody kits to determine VISP. The researchers found that 41.7 percent had VISP, though the occurrence varied across vaccine product types, including 100 percent who received a glycoprotein 140 vaccine, 53.4 percent who received poxvirus either alone or as a boost, 86.7 percent receiving adenovirus 5 product, and 6.3 percent receiving DNA-alone product. VISP most commonly occurred with an HIV 1/2 (rDNA) EIA kit (40.9 percent).

In the second study, Jason S. Haukoos, M.D., of the Denver Health Medical Center, and colleagues analyzed data from four-month intervals of non-targeted opt-out rapid HIV screening in an emergency department or physician-directed diagnostic rapid HIV testing. Non-targeted opt-out screening in conjunction with diagnostic testing was linked to roughly 30 times more HIV tests performed, but only a few more patients were newly identified with infection compared to diagnostic testing alone. Most patients identified with new infections met serological criteria for AIDS at the time of diagnosis.

"The uptake of HIV screening was low in this emergency department-based HIV screening model. Only 24 percent of patients did not opt out of rapid HIV testing. This finding seems to challenge the hope for the opt-out approach in the emergency medicine setting," write the authors of an accompanying editorial. "The opt-out approach is intended to bypass patients' fear of actively accepting HIV testing and instead to allow for passive acceptance. Nevertheless, patients often decline testing based on the belief that they are not at risk for HIV, even if they are."

Several co-authors of the second study disclosed financial relationships with pharmaceutical companies.